Could the solution to our global energy problem be found at sea?
A new development by the United States Department of Energy (DOE) may be a significant step towards utilizing an unexpected reservoir of nuclear fuel - the ocean. In the last five years, the DOE has invested significant resources into recruiting the best minds from American universities and research institutes to find an effective method for the production of uranium from seawater. The impressive research results have been published in the Journal of Industrial & Engineering Chemistry Research.
Uranium is one of the most rare elements on earth, and with specific gravity 18 times greater than water, it is also one of the heavier ones. In addition, uranium is a radioactive element, meaning it spontaneously breaks down to lighter elements, and releases a large amount of energy in the process. At the Earth’s core this process occurs continuously and is one of the factors responsible for its high temperature.
All of these unique characteristics have led to uranium’s commercial exploitation in nuclear reactors to generate electricity, which was first implemented in the fifties of the 20th century in the Soviet Union and the United States. Within the core of a nuclear reactor, there is a controlled disintegration of uranium, similar to the breakdown occurring at Earth’s core. The immense amount of heat emitted from the breakdown process is used to power turbines and generate electricity in a clean manner i.e. with no greenhouse gas emissions or the release of other pollutants into the atmosphere. Ninety nine percent of natural uranium is the relatively stable uranium-238, and about 0.7% is uranium-235, whose nucleus breaks down more easily and so is the preferred form to be used in nuclear reactors. In order to get an effective nuclear reaction, the uranium needs to be enriched (to increase the percent composition of uranium-235), which is a complicated and expensive process.
Today the only source of uranium is from rock mined underground, the contents of which is estimated at several tens of millions of tons and destined to dwindle over the next 200 years. Seawater also contains a natural although low concentration of uranium - more specifically, about 3 parts per billion, or 3 thousandths of a gram of uranium in every liter of seawater. While this is a relatively low concentration, it is the sheer volume of the ocean that can provide us with about 4.5 billion tons of uranium. Overall, the amount of uranium in land resources pales in comparison. Assuming we could get our hands on say half the amount of uranium in the oceans, we could provide the world with nuclear energy for thousands of years.
Uranium as a renewable energy source
New technology is being pursued based on the work of Japanese researchers who discovered amidoxime; a material that can absorb uranium from seawater. In a recent study, American scientists threw several meter-long fibers coated with amidoxime into the seabed and left them there for 50 days. At the end of the test period the researchers were able to produce about 6 grams of uranium for every kilogram of absorbent material. This is the most efficient uranium production from seawater recorded to date.
It should be noted that the process is not yet complete, and is not economically viable given the resources of uranium that still exist in the soil, and whose production cost is about half the cost of extracting uranium from the sea. In addition, fossil fuels like coal, oil and natural gas are still available and are much cheaper than the uranium enrichment process that is required for its use. However, according to Steven Kung from the Ministry of Atomic Energy at DOE, "The discovery of alternatives to uranium mining is a necessary step in planning for the future of nuclear energy." If and when there is a decrease in the price of uranium extraction from the sea, it also has another important advantage against other energy sources – it is renewable! The uranium in the sea water is at equilibrium with the uranium inside the rocks on the bottom of the sea, which themselves contain about one hundred trillion tons of the element. This means that when uranium is sourced from the sea, more uranium will be released from the rocks back into the bottom. Thanks to this renewable cycle, humanity will not be able to empty the uranium reserves in a billion years. Thus giving uranium the status parallel to that of solar energy as a source of clean, renewable energy.
Apart from the not-so-simple economic obstacles, the use of uranium does involve social problems, like the fear that it will be used to make nuclear weapons. In addition, many countries have chosen to significantly reduce the scope of their nuclear energy production due to the risk of nuclear leakage that might occur in an accident or natural disaster. However, if researchers can overcome these obstacles, they might be able to provide a sustainable energy with an unrestricted desire.
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